Decapsulation System

ABSTRACT

A decapsulation apparatus has an etch plate, an off-center etch head having an opening, a cover sealing to the etch plate forming an etching chamber, a gasket surrounding the opening, a ram sealed through the cover, a pressure-controlled source of Nitrogen or inert gas continuously purging the etching chamber at a low gas pressure, a f toggle mechanism mounted to a metal plate t, an etchant supply subsystem comprising sources of etchant solutions, an etchant solution pump, supply passages and controls to select etchants and etchant ratios, and a heat exchanger heating or cooling the etchant solution, etchant waste passages f conducting used etchant away. Etchants are mixed in the passages to the reaction region, and turbulence in the reaction region is promoted by impinging etchant solution on the encapsulated device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is in the field of semiconductor manufacturing andpertains more particularly to methods and apparatus for applying anetchant to decapsulate all or a portion of an encapsulated electronicdevice.

2. Discussion of the State of the Art

Plastic packaging of various electronic devices, including semiconductorchips, is a well-known process that has been practiced for a long time.Typically, an epoxy or other plastic resin is molded around asemiconductor device creating a chip package. The molding protects acentral portion of a lead frame and bonding wires or other connectionsbetween contact pads on the chip or device to inner lead fingers on thelead frame. It is often required to decapsulate such a semiconductorpackage at least in part to allow for device inspection, device testingand, if needed, repair of the chip and or wire bonds to the chip andinner lead fingers after the encapsulation material) covering theseelements is removed.

Most commonly, concentrated acids such as sulfuric acid and fumingnitric acid and other liquid materials are used in the decapsulationprocess to etch the resin material. One challenge in decapsulationsystems of prior art is controlling the exact amount of etchant injectedinto the process. Moreover, a related challenge is preventing damage tothe package under process, including preventing damage to interiorcopper or other metal wires or metal components of the device.

It is desired in some cases that devices which are already attached to aprinted circuit board (PCB) or other substrate be decapsulated withoutremoving the semiconductor device from the PCB or mounting substrate.Removing the solder may create additional defects. Additionaloperational artifacts can be confused with defects built into the deviceor defects resulting from mounting the device to the PCB or substrate.

Prior art decapsulating systems are also limited in the size of devicethat can be mounted by the size of the etch plate and safety cover.Prior art systems have the etch plate or etch head centrally located.Therefore to accommodate, for example, a six inch square sample, theetch plate and cover must be over 12 inches square, lending to a systemthat is too large to handle the pressurization on the cover and etchplate. Some systems use an etch plate manufactured of virginpolytetrafluoroethylene (PTFE) and supported only on the periphery ofthe system. The higher pressure range may damage or deform the etchplate.

Yet a further limitation of prior decapsulating systems is that due totriboelectric characteristics of the PTFE etch plate, high electrostaticdischarge from the plate may occur during movement of the device fromthe plate and fixture. Furthermore, if the device is mounted to a PCB orsubstrate there is a possibility of electrostatic discharge (ESD) damageto PCB interconnects and the clamping apparatus holding the device coverdown.

Therefore, what is clearly needed is a decapsulation system thateliminates the problems described above.

BRIEF SUMMARY OF THE INVENTION

In one embodiment of the invention a decapsulation apparatus is providedcomprising an etch plate supporting substantially off-center an etchhead having an opening for exposing a portion of an encapsulated deviceto etchant solution, a vertically translatable cover sealing to the etchplate, the etch plate and cover forming an etching chamber over the etchhead, a gasket on the etch head surrounding the opening, the gasket forsealing an encapsulated device or a portion of a printed circuit board(PCB) supporting an encapsulated device to the etch head, exposing theencapsulated device through the opening to etchant solution, a rammechanism sealed through the vertically-translatable cover, adapted totranslate a ram downward to urge the encapsulated device or PCB againstthe gasket, a pressure-controlled source of Nitrogen or inert gascoupled into the etching chamber, continuously purging the etchingchamber at a low gas pressure, a force-producing, locking togglemechanism mounted to a metal plate to which the etch plate is alsomounted and a top of the cover, the toggle mechanism adapted to exert adownward force on the cover, to keep the cover sealed against upwardforce exerted by the nitrogen supplied to the etch chamber, themechanism releasable to open the cover, an etchant supply subsystemcomprising one or more sources of etchant solutions, an etchant solutionpump, supply passages to a reaction region adjacent the encapsulateddevice, and controls to select etchants and etchant ratios, a controlledheat exchanger through which the supply passages pass, heating orcooling the etchant solution transported to the enapsulated device, oneor more etchant waste passages from the reaction region for conductingused etchant away from the encapsulated device, wherein etchants aremixed in the passages to the reaction region, and turbulence in thereaction region is promoted by impinging etchant solution on theencapsulated device.

In one embodiment the controlled heat exchanger utilizes electricheaters and thermoelectric cooling elements to control temperature ofthe etchant mixture to temperatures between 0 degrees Celsius and 250degrees Celsius. Also in one embodiment the etch plate is supported byboth a metal plate to which the lift mechanism is mounted and asecondary metal support between the heat exchanger and etch plate so asto prevent deformation of the etch plate. Also in one embodiment thetoggle mechanism for the safety cover comprises two synchronized liftarms operated by two independent toggle mechanisms. Also in oneembodiment the two independent toggle mechanisms are synchronized by asingle lever and link with a travel stop for the single lever.

In one embodiment of the invention the single lever has its rotationalmotion reversed by a two gear mechanism. Also in one embodiment the twolift arms function as springs to maintain force on the safety cover.Also in one embodiment additional Bellville springs are used to augmentthe spring qualities of the lift arms Also in one embodimentcontinuously purging with nitrogen or other gas is accomplished byintermittently introducing high pressure dry nitrogen or other gasdirectly into the etching chamber. And in one embodiment the pressure ismaintained in the etching chamber by introducing high pressure drynitrogen or other gas when the pressure in the chamber is less than apre-programmed level and terminating the introduction when the pressurein the chamber reaches a level somewhat greater that the preprogrammedlevel.

In an alternative aspect of the invention a method for decapsulating isprovided comprising the steps placing an encapsulated device or aprinted circuit board including an encapsulated device on a gasket on anetch head supported substantially off-center on an etch plate, the etchhead and gasket having an opening exposing the encapsulated device to areaction region below the etch head, sealing a vertically-translatablecover to the etch plate with a toggle mechanism mounted to a metal plateto which the etch plate is mounted, the etch plate and cover forming anetching chamber over the etch head, urging the encapsulated deviceagainst the gasket by a ram mechanism operating sealed through thecover, continuously purging the etching chamber with apressure-controlled source of Nitrogen or inert gas, delivering anetchant solution to the reaction region from a controlled pump drawingetchant solution in a preset ratio from one or more sources, heating orcooling the etchant solution in passages leading to the reaction regionthrough a heat exchanger, and removing used etchant solution from thereaction region through one or more waste passages.

In one embodiment of the method a portion of the etchant is oscillatedout of and back into the reaction region, digesting resinous material onthe encapsulated device to form a hole in the resinous material. Also inone embodiment the temperature of the etchant mix is controlled to be ina range of from 0 degrees Celsius to 250 degrees Celsius. Also in oneembodiment multiple interlocking gaskets are used to seal the PCB orencapsulated device to the etch head.

In one embodiment of the method the controlled pump draws etchantsolution from two separate sources, one providing fuming sulphuric andthe other fuming nitric acid, shear mixes the solution in the passagesthrough the heat exchanger, and oscillates a portion of the mixture intoand back out of and back into the reaction region. Also in oneembodiment the ratio of nitric to sulphuric acid in the etchant solutionis controlled, and the heat exchanger is controlled to maintain thetemperature of the etchant solution above the known freezing temperatureof the etchant solution at the ratio selected and controlled. Also inone embodiment the ratio of nitric to sulphuric acid in the etchantsolution is controlled, and the heat exchanger is controlled to maintainthe temperature of the etchant solution below the known boilingtemperature of the etchant solution at the ratio selected andcontrolled. In one embodiment the ratio of nitric to sulphuric acid iscontrolled to be 0:1, 1:1, 2:1, 3:2, 3:1, 7:2, 4:1, 5:1, 6:1, 9:1, or1:0. And in one embodiment multiple interlocking gaskets are used toseal the encapsulated device or PCB to the etch head, wherein eachgasket has a rectangular recess that precisely fits the next highergasket, each gasket is larger than the next higher gasket, and the topgasket has a recess that closely fits the encapsulated device or PCB.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a partial section view of a decapsulating system according toan embodiment of the invention.

FIG. 2 is an overhead view of the etch plate of FIG. 1 and supportinghardware.

FIG. 3 is an overhead view of the decapsulator cover lifting andclamping assembly.

FIG. 4 is an elevation view of the cover lifting assembly of FIG. 3.

FIG. 5 is an elevation view of the linkage structure of the liftingassembly of FIG. 3 in clamped and locked position.

FIG. 6 is a plan view of the linkage of FIG. 5 in an unclasped orunlocked position.

FIG. 7 is a plan view of a PCB or substrate containing a mountedsemiconductor device mounted for decapsulation on the device of FIG. 1in a multiple gasket configuration according to an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

In various embodiments described in enabling detail herein the inventorprovides a unique system for decapsulating semiconductor devicesincluding devices mounted to printed circuit boards or other substratesand with other components mounted. The present invention is describedusing the following examples, which may describe more than one relevantembodiment falling within the scope of the invention.

FIG. 1 is a partial section view of a decapsulating system 100 accordingto an embodiment of the invention. Decapsulation system 100 includes anetchant delivery pump 101. Pump 101 delivers one or a mix ofdecapsulation etchant into a decapsulator heat exchanger 119 via adelivery line 106. Pump 101 includes a supply line 103 to an etchantsource and a supply line

105 to a different etchant source (etchant source containers notillustrated). Decapsulation system 100 includes an etch head 115 mounted(clamped in one implementation) to an etch plate 114. Etch head 115supports device mounting apparatus enabling mounting of a semiconductordevice that is in turn mounted to a PCB or similar substrate. One suchdevice is depicted herein as a semiconductor device or package 116.Package 116 is an encapsulated package and may require decapsulation atleast in part to reveal components for quality or lot control (QC)testing and repair if required. Etch head 115 may be clamped to heatexchanger 119 by a retainer ring 134. Etch head 115 may be sealed toetch plate 114 via an O-ring seal.

System 100 includes an etch chamber cover 108 that fits over etch plate114 to create an etching chamber that can withstand high pressurization.Cover 108 may be locked or clamped down over etch plate 114 using aunique clamping apparatus that is described in detail later in thisspecification. Cover 108 is moveable and may be unclamped and lifted offetch plate 114 using the same apparatus described above for clamping thecover onto the etch plate. In this example package 116 rests on a gasket129. Cover 108 may be sealed to etch plate 114 using an O-ring seal 107.

When cover 108 is clamped in place over etch plate 114, an etch chamber130 is created.

Etch head 115 may be clamped over a heat exchanger 119 in system 100.Etch head 115 has a passage 135 adapted to deliver etchant and dispensesof waste etchant through two waste passageways 122. Passages 135 and 122extend into the heat exchanger with waste passages 122 extending out ofthe heat exchanger. System 100 includes a ram nose 132. Ram nose 132 isdriven toward device package 116 by a ram piston 111 against a ram 131to which ram nose 132 is threaded.

Pressure for driving the ram may be supplied by a pressurized source ofgas, such as inert nitrogen gas. A valve mechanism 123 hosting twoelectrically operated valves 124 and 125 may be provided to meterpressurized nitrogen to pressure chamber 112. Valve 124 may be operatedto allow nitrogen gas to pass through a tube 113 fitted onto apassageway into the pressure chamber. Nitrogen gas may be used topressurize chamber 112 to drive ram nose 132 against the device packagesealing the device package to gasket 129 and etch head 115. A ram returnspring 110 is provided to withdraw ram nose 132 from the device packagewhen pressure in chamber 112 is released.

Ram piston 111 and ram 131 may be housed within a ram mount 133. Cover108 may be fixed or otherwise attached to a cover mount 109. In oneimplementation, ram mount 133 includes a mounted optical position sensor(not illustrated) that may detect full extension of ram 132 and rampiston 111. Valve plate 123 includes an electrically operated valve 125that may allow passage of nitrogen from the same source through a tube134 into the etch chamber 130 through etch plate 114 during purgeoperations. When valve 124 is not activated, the volume of chamber 112and tube 113 may be vented to the environment.

System 100 includes a pressure transducer 136 having connection to etchplate 114 via a fitted tube 121. In operation, pressure within chamber130 is monitored by transducer 136. Pressure threshold measurements maybe observed for both high pressure states and low pressure states. Forexample, if pressure within chamber 130 drops below a minimum thresholdas measured by transducer 136, the electronic controller or controlsystem may open valve 125. When the pressure in chamber 130 exceeds acertain pressure threshold value as measured by the transducer, thecontroller or control system may close valve 125. In this way thepressure within chamber 130 may be managed to be within an expectedrange that is lower than the pressure of the source tank or container ofnitrogen.

Pump 101, as described above, has an etchant delivery tube 106 leadingfrom pump 101 into heat exchanger 119. Tube 106 has a flanged end (notvisible) that may be sealed via an P ring against etch head 115. Tube106 connects to the source delivery passage 135 in the heat exchanger,which in turn enters the etch head. Pump 101 draws etchant from supplycontainers through lines 103 and 105 and pumps the etchant into line 106for delivery to the decapsulator. Tube 104 is a nitrogen purge line.When the etchant delivery is in heat exchanger 119, it may assume atemperature similar to that of the heat exchanger.

Heat exchanger 119 may be heated by one or more electrically-controlledheating devices 136 and may be cooled by a thermoelectric coolingassembly 120. A control system may be used to monitor and to control oradjust the temperature of the heat exchanger. The desired temperaturevalue may be below ambient temperature, as low as zero degrees Celsius(C.) for packages containing copper metallization. The temperature mayalso be maintained above the boiling points of the etchants, such as attwo hundred and fifty degrees C. for packages not containing any coppermetallization.

Pump 101 may be controlled to select either one or the other enchantsupply tubes 103 or 105 to activate etchant delivery at each deliverycycle. In this way pump 101 may deliver one etchant at a time or anyratio of mixed etchants. Etchant delivery cycles may be very rapid andunder a relatively high pressure. Etchant mixes may therefore be madehomogenous through shear mixing within tube 106 leading into heatexchanger 119. Each fresh delivery of etchant during a decapsulation runagitates etchant already in contact with the etch cavity on the devicebeing processed. Some portion of etchant in contact with the package maybe displaced into the waste or passages 122 in etch head 115.Passageways 122 extend from the etch cavity at the top of etch head 115through the etch head, through heat exchanger 119, throughthermoelectric cooling device 120, and through a waste junction block128.

Pump 101 may be a diaphragm dispensing pump capable of delivering highvelocity pulses of etchant to the etchant heat exchanger. Pump 101 hascapability of pumping etchant from multiple sources on a cycle-by-cyclebasis allowing for generation of various mix ratios of the etchants. Theprocess in one embodiment uses fuming nitric acid, fuming orconcentrated sulfuric acid, or a mixture of the two acids at acontrolled temperature from the boiling point of the etchant or mixturedown to below ambient temperatures.

High velocity of the pulses produces shear mixing in the etchant heatexchanger and creates turbulence in the etch cavity formed on thepackage exterior surface by reaction of the etchant solution with theresinous material. This turbulence provides for removal of non-reactiveelements of the encapsulating resin from the etch face resulting inexposure of more of the reactive material for faster etching. The pumpis also capable of withdrawing etchant from the etch cavity to againdeliver the etchant with high velocity pulses. This partial recycling ofthe etchant reduces etchant usage while maintaining delivery of highvelocity pulses at a high rate.

Waste passages 122 may be combined in waste junction block 128 into onestream transported through a waste tube 127. Combined waste then travelsthrough tube 127 and into a second heat exchanger 102 that returns thetemperature of the heated waste back to near ambient temperature. O-ringseals provide connection sealing for the waste tubes 122 at theappropriate junctions with different components. Output from second heatexchanger 102 may lead to a waste container (not illustrated) adapted tostore waste etchant materials.

In one embodiment, etch plate 114 is manufactured of carbon filled-PTFEand is attached to a top plate (see FIG. 2) by screws threaded intoinserts (not illustrated) installed in etch plate 114. The central areaof the top plate may be relieved by machining to an extent so that heatexchanger 119 and thermoelectric device 120 may be directly affixed toetch head 115. In a preferred embodiment, Etch head 115, heat exchanger119, and thermoelectric assembly 120 may be assembled onto etch plate114 and placed on the top plate as a single assembly.

Etch plate 119 in one embodiment is made of carbon-filled PTFE making itstronger and more dimensionally stable than virgin PTFE. The etch plateis supported over most of its area and a separate reinforcing plate (topplate) is mounted to the bottom side to limit deformation. In additionthe carbon-filled PTFE is conductive, eliminating static voltagegeneration. The clamping mechanism may be manufactured of conductivepoly ether ether ketone (PEEK) eliminating discharges from the componentto the clamping device, and may be connected to earth ground by contactwith the ram return spring, the stainless steel ram mount, and throughthe cable earth connection to the cover mount.

In one embodiment a support plate 117 is provided to minimize tendencyfor the etch plate to become warped or otherwise compromised due to highpressure in etch chamber 130 and the down force of ram nose 132 ondevice package 116. Support plate 117 may be fixed or otherwise attachedbetween heat exchanger 119 and etch plate 114. Support plate 117 may bemounted to the etch plate 114 by screws threaded into inserts installedin the etch plate. In one embodiment PTFE spacers may be placed betweenheat exchanger 119 and support plate 117. The larger area of cover mountplate 109 fairly distributes the downward force over a large area ofcover 108 reducing deflection of the cover.

It is noted herein that heat exchanger 119 may incorporate a serpentineof etchant-resistant tubing that is encased in an aluminum block. Thisaluminum block may also contain electric heaters and has contact withthermoelectric modules that can either heat or cool the aluminum block.An electronic control mechanism operates the heaters and thermoelectricmodules to maintain a constant temperature of the aluminum block. Thetemperature can be controlled from well below ambient temperature thatis, less than 15 degrees C., to well above the boiling point of theetchant, that is, more than 250 degrees C.

FIG. 2 is an overhead view of the etch plate assembly of FIG. 1 andsupporting hardware. In this example support plate 117 is bolted to etchplate 114. Etch plate 114 includes a passageway 203 within the etchplate leaving a portion unsupported. Support plate 117 provides addedsupport for this portion. In this example a top plate 207 may also beprovided to strengthen etching plate 114. Etch head 115 is positionedoffset from center on support plate 117. Threaded inserts 204 areprovided to enable attachment of etch plate 114 to top plate 207.Threaded inserts 201 are provided to enable support plate 117 and heatexchanger (119 FIG. 1) to be attached to etch plate 114.

A peripheral groove 202 is provided in etch plate 114 and is adapted toseat a seal gasket, such as gasket 107 of FIG. 1, providing a seal forcover 108. Etch plate 114 includes a threaded opening 205 and a threadedopening 206. These openings facilitate attachment of tubes like tube 134and tube 121. In this example, the offset from center location of etchhead 115 facilitates PCB-mounted devices up to six inches square with asmaller cover plate. Prior art systems are centrally oriented withrespect to the etch head position requiring a much larger etch plate andsafety cover of up to twelve inches square to accommodate devices of thesame size (6 inches). The smaller footprint of the etching system inembodiments of the invention helps to reduce possible deformation anddamage to the plate and cover under high pressure in the etch chamber.

FIG. 3 is an overhead view of lifting and clamping assembly 300.Assembly 300 includes a lever or lift arm 301. Lift arm 301 may bemanually operated to open and remove cover (108) or to clamp cover (108)to etch plate 114. Lift arm 301 is fixed to a geared shaft or axle 302.Axle 302 is housed within a bearing block 303 and a bearing block 306.Axle 302 has a fixed gear 304. Gear 304 is meshed with an adjacentfitted gear 305. Gear 305 is fixed to a second shaft or axle 307. Axle307 is housed within bearing block 306.

Operation of lever arm 301 causes rotation of shaft 302 and concurrentgear interaction between meshed gears 304 and 305 to produce rotation ofshaft or axle 307 in the opposite direction of the first rotationdirection of shaft 302. Assembly 300 includes a lever 313 that isaffixed in this example to shaft or axle 307. Mechanism 300 includesrotatable links 312 adapted to transmit the motion of lever 301 to twotoggles (open, lock) made up of two links (not visible in this view)described further below. Mechanism 300 includes parallel cover arms 310that are fixed to cover mount 316, which may be analogous to mountingplate 109 of FIG. 1. Cover arms 310 are thinner at arm extensions 310,which are mounted to cover mount.

Lifting and clamping assembly 300 further includes support blocks 309.Support blocks 309 are each adapted to support one cover arm 310 via afreely rotatable shaft or pin inserted through the cover arm and thesupport block. The cover arms may be freely rotatable at the insertedshaft or pin (not illustrated). The free ends of cover arms 310 areconnected to the top of a cover mount 316 analogous to cover mount 109of FIG. 1.

In operation when lever arm 301 is moved, its motion may be transferredthrough meshed gears 304 and 305, to lever 313. Lever 313 acts throughlinks 312 and 315 (toggles) to move pivotally-mounted cover arms 310. Itis noted herein that in this example all of the mechanism supportarchitecture, such as cover arm supports 309 for example, are fixed totop plate 308. The toggle operation runs in parallel with the toggles(links 311 and 315) locking to close the cover over the etch plate orunlocking to raise the cover up and away from the etch plate. Plate 308includes a fixed travel stop 314 that may prevent excess range of motionfor lever 313.

In one example lifting upward on lever or lift arm 301 may cause thecover mount to rise, raising the cover up and off of the etch platetypically after a process is complete and a purging operation has beenperformed. Cover arms 310 supply the downward force required to holdsafety cover (108) in place against the etch plate or top plate. Thelarge footprint of the cover mount compared to the cover results indistribution of force over a large area of the safety cover (108)reducing any deflection occurring during clamp down (locked) togglestate.

FIG. 4 is an elevation view of the cover lifting assembly of FIG. 3.Some of the components depicted in FIG. 3 are not visible in this view.As described previously, all hardware may be supported by top plate 207.A travel stop 314 is provided in one embodiment and mounted to top plate207. Travel stop 314 limits the pivotal motion range of the pivotingsafety cover (108).

Top plate 207 shows a support block 412 that hosts a pair of links (414)and (312) that are pivotally connected and are used to drive a togglepair of links 311 and 409. One end of link 414 is be mounted to the rearside of support plate 412. Link 312 may be an intermediary linkconnected at one end to lever link 414, Link 414 has a fixed connectionto a shaft (307) operated by a lift arm like lift arm 301. The motion ofthe lift arm causes the shaft to move, resulting in movement of link414. Link 414 has a rotatable connection to intermediary link 312. Link312 has a rotatable connection to a pair of (toggle) links including alink 312 and a link 409. Toggle links 311 and 409 form a toggle atcertain positions, toggle referring herein to a switch like state forthe chamber cover 108.

In this example, toggle links 311 and 409 are vertically aligned,signifying that cover 108 is down and locked. The other of two togglestates are “unlocked” or “unclamped”. Links 409 and 311 are rotatablyconnected together. Link 411 is rotatably connected to a toggle supportblock 411 on the end opposite of link 311. Link 311 has a rotatableconnection to cover arm 310. Cover arm 310 has a thinner extension 317(cross hatched). The end of cover arm extension 317 may be fixed tocover mount 109 via a tension screw 404 and a “Bellville” disc spring403.

In this clamped position safety cover 108 is forced into contact withetch plate (114, FIG. 1) compressing seal 107 (FIG. 1) resulting in asubstantially gas tight seal between the cover and etch plate. In oneimplementation a minimum pressure for the etch chamber may beapproximately 2 pound per square inch (2 PSI). When the etch chamber 34(FIG. 1) is pressurized with minimally 2 PSI, the upward force on thesafety cover is nominally 150 lb (68 Kg). At the minimum of 2 PSI, thenominal upward force on safety cover 108 is about 150 pounds. Inaddition, downward force of the ram body (110, FIG. 1) pushes the ramnose (132, FIG. 1) into contact with the semiconductor device to bedecapsulated. This downward force results in an equal and oppositeupward force on exerted on safety cover 108. The total nominal upwardforce on the cover is about 162 lbs. in this circumstance.

The downward force translated to cover mount 109 by cover arms 310 isgreater than the upward combined force of 162 pounds. The downwardclosing force transmitted by the two cover arms is nominally 180 pounds,which is greater than the upward force on the safety cover plus the downforce required to establish a seal between etch plate 114 and safetycover 108. As described further above the toggle links 311 and 409 areused to clamp the cover down and force up the rear end of the cover armsin parallel.

Cover arms 310 are pivotally mounted on cover arm support block 309. Theapplied force results in some deflection of the cover arms 310 along thethinner extensions 317. In addition there are in one embodiment severalBellville disc springs 403 located at the mounting site of each of thearms with the cover mounting plate. A shoulder screw 404 may be providedto loosely mount cover 108 via cover mount 109 to the cover arms (310).In this way safety cover 108 may freely move or deflect while downwardpressure is applied. Such movement helps to get better sealing resultsagainst the etch plate.

FIG. 5 is an elevation view of the linkage structure of the liftingassembly of FIG. 3 in clamped and locked position. FIG. 6 is anelevation view of the linkage of FIG. 5 in an unclamped position.

Referring now to FIG. 5, toggle links 311 and 409 are vertically alignedas described for a clamped or locked position where the safety cover isclosed over the etch plate. Link 313 functions as a lever being fixed atone end to a shaft extending through support block 412. Rotation of theshaft in a counter clockwise direction as viewed from this perspectiveforces intermediate link 312 to pull at the junction point shared withtoggle links 311 and 409 resulting in a forced alignment of the togglelinks vertically.

It is noted herein that each toggle link is manufactured to be over aspecific dimension from center line to center line of the toggleopenings or the functional length dimension of each link. In this waythe links lock, putting downward pressure on the safety cover throughthe cover arm extensions. In one implementation a magnet 516 is providedand disposed at a strategic location on top plate 207. A second magnet517 may be provided at a strategic location on toggle link 409. When thelink apparatus is in the locked or clamped position as depicted in thisexample, the magnets 516 and 517 are held separate from one another. Thepivot point for cover arm 310 is at attachment block 309 where the pivotpin is mounted through the cover arm.

Referring now to FIG. 6, toggle links 311 and 409 have been urged out ofa vertically-aligned position associated with a closed and sealed safetycover. Reverse direction of motion applied to a lift arm (301, FIG. 3)functions to break the link alignment by pushing toggle links 311 and409 with lever-driven intermediate link 312. The result is lifting ofthe safety cover via pivoting of cover arm 310 about the pivot point.

When the mechanism is brought to the full cover-open position, magnet517 on toggle link 409 makes contact with magnet 516 mounted on topplate 207. The magnetic attraction between the magnets keeps the safetycover in the full open (pivoted) position. Referring now to FIG. 3,travel stop 314 includes an adjustable contact mechanism that may makephysical contact with lever (fixed shaft link) 313 when the mechanism isin the locked down position of FIG. 5.

Referring again to FIG. 3, the amount of force exerted on lift arm 301to close and seal the safety cover over the etch plate (114, FIG. 1) mayvary considerably depending upon the position of the lift arm along therotational path. The amount of force required to move the lift armincreases proportionally with the position of the arm along therotational path such that the maximum required force on the lift armoccurs when the toggle links (311, and 409), lever 313 and intermediatelink 312 are at full extension. The manufactured lengths of the linksand lever function to set the desired force ratio.

In this example, a maximum extension force of 9 pounds is required toproduce the approximate 180 pound downward force one the cover mount andcover through the extensions of the cover arms. By controlling thedimensional tolerances of the links with respect to functional length(center line to center line of link openings and the link connectinghardware (openings and pins), the desired force downward force for thelocking mechanism may be configured.

FIG. 7 is a sectioned elevation view of a PCB or substrate hosting amounted semiconductor device for decapsulation on the apparatus of FIG.1 in a multiple gasket configuration according to an embodiment of thepresent invention. In this example a PCB 701 has a semiconductor device702 mounted thereon. PCB 701 also includes at least one other component706 mounted thereon. The additional component or components mounted tothe PCB require that the PCB not be positioned too close to the etchhead so as not to disturb that component or components.

Semiconductor device 702 may be soldered to PCB 701 along with othercomponents such as component 706. In this example the presence of theadditional components requires that the device be a certain largerdistance from etch head 115. To create a larger distance between etchhead 115 and device 702, gasket stacking is employed in one embodiment.In this embodiment there are three gaskets. A gasket 705 is positionedon etch head 115. A second gasket 704 is positioned over gasket 705.

A physical feature or depression on gasket 705 enables gasket 704 to becentered over and fitted onto gasket 705. A third and top gasket 703fits into a physical feature on the top surface of gasket 704. Thephysical features on the gasket surfaces may be molded pockets designedand of a size to fit another specific gasket. On the top surface ofgasket 703, a physical feature or pocket is provided to accept device702.

In one implementation the stack of gaskets may include several gasketsstacked on top of one another. With for example 8 gaskets of typicalthickness, the added distance between the etch head and device may befour tenths of an inch or so (approximately 10 mm). In an implementationusing multiple stacked gaskets, each of the gaskets used in theapplication require a central opening the size of the decapsulationwindow or area on the device to prevent any part of a gasket obstructingthe flow of etchant during the decapsulation process.

It will be apparent to one with skill in the art that the decapsulationapparatus of the invention may be provided using some or all of thementioned features and components without departing from the spirit andscope of the present invention. It will also be apparent to the skilledartisan that the embodiments described above are specific examples of asingle broader invention that may have greater scope than any of thesingular descriptions taught. There may be many alterations made in thedescriptions without departing from the spirit and scope of the presentinvention.

It will be apparent to the skilled person that the arrangement ofelements and functionality for the invention is described in differentembodiments in which each is exemplary of an implementation of theinvention. These exemplary descriptions do not preclude otherimplementations and use cases not described in detail. The elements andfunctions may vary, as there are a variety of ways the hardware may beimplemented and in which the software may be provided within the scopeof the invention. The invention is limited only by the breadth of theclaims below.

1. A decapsulation apparatus comprising: an etch plate supporting anetch head. off center of the etch plate, having an opening for exposinga portion of an encapsulated device to etchant solution; a verticallytranslatable cover sealing to the etch plate, the etch plate and coverforming an etching chamber over the etch head; a gasket on the etch headsurrounding the opening, the gasket for sealing an encapsulated deviceor a portion of a printed circuit board (PCB) supporting an encapsulateddevice to the etch head, exposing the encapsulated device through theopening to etchant solution; a ram mechanism sealed through thevertically-translatable cover, adapted to translate a ram downward tourge the encapsulated device or PCB against the gasket; apressure-controlled source of Nitrogen or inert gas coupled into theetching chamber, continuously purging the etching chamber at a low gaspressure; a force-producing, locking toggle mechanism mounted to a metalplate to which the etch plate is also mounted, and a top of the cover,the toggle mechanism adapted to exert a downward force on the cover, tokeep the cover sealed against upward force exerted by the nitrogensupplied to the etch chamber, the mechanism vertically releasable toopen the cover; an etchant supply subsystem comprising one or moresources of etchant solutions, an etchant solution pump, supply passagesto a reaction region adjacent the encapsulated device, and controls toselect etchants and etchant ratios; a controlled heat exchanger throughwhich the supply passages pass, heating or cooling the etchant solutiontransported to the encapsulated device; one or more etchant wastepassages from the reaction region for conducting used etchant away fromthe encapsulated device; wherein etchants are mixed in the passages tothe reaction region, and turbulence in the reaction region is promotedby impinging etchant solution on the encapsulated device.
 2. Thedecapsulation apparatus of claim 1 wherein the controlled heat exchangerutilizes electric heaters and thermoelectric cooling elements to controltemperature of the etchant mixture to temperatures between 0 degreesCelsius and 250 degrees Celsius.
 3. The apparatus of claim 2 wherein theetch plate is supported by both a metal plate to which the lockingtoggle mechanism is mounted and a secondary metal support between theheat exchanger and etch plate so as to prevent deformation of the etchplate.
 4. The apparatus of claim 1 wherein the toggle mechanism for thesafety cover comprises two synchronized lift arms operated by twoindependent toggle mechanisms.
 5. The apparatus of claim 4 wherein thetwo independent toggle mechanisms are synchronized by a single lever andlink with a travel stop for the single lever.
 6. The apparatus of claim5 wherein the single lever has its rotational motion reversed by a twogear mechanism.
 7. The apparatus of claim 4 where the two lift armsfunction as springs to maintain force on the safety cover.
 8. Theapparatus of claim 7 where additional Bellville springs are used toaugment the spring qualities of the lift arms
 9. The apparatus of claim1 wherein the continuously purging with nitrogen or other gas isaccomplished by intermittently introducing high pressure dry nitrogen orother gas directly into the etching chamber.
 10. The apparatus of claim9 wherein the pressure is maintained in the etching chamber byintroducing high pressure dry nitrogen or other gas when the pressure inthe chamber is less than a pre-programmed level and terminating theintroduction when the pressure in the chamber reaches a level greaterthat the preprogrammed level. 11-19. (canceled)